High bandwidth memory (HBM) bandwidth aggregation switch

ABSTRACT

Methods and apparatus are described for adding one or more features (e.g., HBM) to a qualified SSI technology programmable IC region by providing an interface (e.g., an HBM buffer region with a switch network) between the added feature device and the programmable IC region. One example IC package generally includes a package substrate; at least one interposer disposed above the package substrate; a programmable IC region disposed above the interposer; at least one fixed feature die disposed above the interposer; and an interface region disposed above the interposer and configured to couple the programmable IC region to the fixed feature die via a first set of interconnection lines routed through the interposer between a first plurality of ports of the interface region and the fixed feature die and a second set of interconnection lines routed between a second plurality of ports of the interface region and the programmable IC region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. patent application Ser. No. 15/237,384, filed Sep. 23, 2016 and entitled “STANDALONE INTERFACE FOR STACKED SILICON INTERCONNECT,” which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Examples of the present disclosure generally relate to integrated circuits (ICs) and, more particularly, to integrated circuit packaging using stacked silicon interconnect (SSI) technology and to an interface between a programmable IC die and a fixed feature die.

BACKGROUND

Electronic devices (e.g., computers, laptops, tablets, copiers, digital cameras, smart phones, and the like) often employ integrated circuits (ICs, also known as “chips”). These integrated circuits are typically implemented as semiconductor dies packaged in integrated circuit packages. The semiconductor dies may include memory, logic, and/or any of various other suitable circuit types.

Many integrated circuits and other semiconductor devices utilize an arrangement of bumps, such as a ball grid array (BGA), for surface mounting packages to a circuit board (e.g., printed circuit board (PCB). Any of various suitable package pin structures, such as controlled collapse chip connection (C4) bumps or microbumps (as used in stacked silicon interconnect (SSI) applications), may be used to conduct electrical signals between a channel on an integrated circuit (IC) die (or other package device) and the circuit board on which the package is mounted.

SUMMARY

One example of the present disclosure is an integrated circuit (IC) package. The IC package generally includes a package substrate; at least one interposer disposed above the package substrate and comprising a plurality of interconnection lines; a programmable IC die disposed above the interposer; a fixed feature die disposed above the interposer; and an interface die disposed above the interposer and configured to couple the programmable IC die to the fixed feature die using a first set of interconnection lines routed through the interposer between the programmable IC die and the interface die and a second set of interconnection lines routed through the interposer between the interface die and the fixed feature die.

Another example of the present disclosure is a method of fabricating an integrated circuit package. The method generally includes providing a mask for a programmable IC die paired with an interface die, the interface die for coupling the programmable IC die to a fixed feature die; generating, using the mask, a wafer having a plurality of the paired programmable IC and interface dies; dicing the wafer to detach a wafer section comprising one of the plurality of the paired programmable IC and interface dies; and disposing the wafer section above an interposer comprising a plurality of interconnection lines, wherein a first set of the interconnection lines is routed through the interposer for electrically connecting the paired programmable IC and interface dies in the wafer section and wherein a second set of the interconnection lines is routed through the interposer for electrically connecting the interface die and the fixed feature die.

Yet another example of the present disclosure is an integrated circuit package. The package generally includes a package substrate; at least one interposer disposed above the package substrate and comprising a plurality of interconnection lines; at least one field programmable gate array (FPGA) die disposed above the interposer; one or more high bandwidth memory (HBM) dies disposed above the interposer; and an HBM buffer die disposed above the interposer and configured to couple the FPGA die to the one or more HBM dies using a first set of interconnection lines routed through the interposer between the FPGA die and the HBM buffer die and a second set of interconnection lines routed through the interposer between the HBM buffer die and the one or more HBM dies. For some examples, the FPGA die and the HBM buffer die share the same wafer-level substrate. For some examples, the FPGA die and the HBM buffer die are separated on the wafer-level substrate by a scribe line.

Yet another example of the present disclosure is a wafer. The wafer generally includes a plurality of logic regions, wherein each logic region comprises a programmable IC die paired with an interface die, the interface die for coupling the programmable IC die to a fixed feature die.

Yet another example of the present disclosure is an IC package. The IC package generally includes a package substrate; at least one interposer disposed above the package substrate; a programmable IC region disposed above the interposer; at least one fixed feature die disposed above the interposer; and an interface region disposed above the interposer and configured to couple the programmable IC region to the fixed feature die via a first set of interconnection lines routed through the interposer between a first plurality of ports of the interface region and the fixed feature die and a second set of interconnection lines routed between a second plurality of ports of the interface region and the programmable IC region.

Yet another example of the present disclosure is a method of fabricating an IC package. The method generally includes providing a mask for a programmable IC region paired with an interface region, the interface region for coupling the programmable IC region to at least one fixed feature die; generating, using the mask, a wafer having a plurality of the paired programmable IC and interface regions; dicing the wafer to detach a wafer section comprising one of the plurality of the paired programmable IC and interface regions; and disposing the wafer section above an interposer, wherein a first set of interconnection lines is routed through the interposer for electrically coupling a first plurality of ports of the interface region and the fixed feature die and wherein a second set of interconnection lines electrically couples a second plurality of ports of the interface region to the programmable IC region of the paired programmable IC and interface regions in the wafer section.

Yet another example of the present disclosure is a wafer. The wafer generally includes a plurality of logic regions, wherein each logic region comprises a programmable IC region paired with an interface region, the interface region for coupling the programmable IC region to a fixed feature die and comprising a first plurality of ports corresponding to the fixed feature die and a second plurality of ports corresponding to the programmable IC region.

These and other aspects may be understood with reference to the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to examples, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical examples of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective examples.

FIG. 1 is a block diagram illustrating an example architecture for a programmable device.

FIG. 2 is a cross-sectional view of an example integrated circuit (IC) package utilizing stacked silicon interconnect (SSI) technology, in accordance with the prior art.

FIGS. 3A and 3B illustrate a top view and a cross-sectional view, respectively, of a portion of an example IC package comprising a programmable IC die coupled to a fixed feature die via an interface die, in accordance with examples of the present disclosure.

FIG. 4 illustrates an example mask for a pair of logic regions, each logic region including a programmable IC die and a high bandwidth memory (HBM) buffer die, in accordance with an example of the present disclosure.

FIG. 5A is a top view of a wafer with programmable IC dies paired with HBM buffer dies, illustrating the scribe cuts where the HBM buffer dies are separated from the programmable IC dies to create logic regions, in accordance with an example of the present disclosure.

FIG. 5B is a top view of the wafer of FIG. 5A, illustrating the scribe cuts where the wafer is diced, leaving the HBM buffer die paired with the programmable IC die to create a logic region with an HBM interface, in accordance with an example of the present disclosure.

FIG. 6 illustrates a top view of a portion of an example IC package utilizing SSI technology comprising a first logic region, a second logic region with an HBM interface, and HBM dies, in accordance with an example of the present disclosure.

FIG. 7 is a block diagram of an example HBM buffer die, in accordance with an example of the present disclosure.

FIG. 8 is a flow diagram of example operations for fabricating an IC package, in accordance with an example of the present disclosure.

FIG. 9 is a block diagram of an example HBM buffer region in which each programmable IC interconnect channel is connected to one and only one HBM channel, in accordance with an example of the present disclosure.

FIG. 10 is a block diagram of an example HBM buffer region in which one programmable IC interconnect channel has access to all the HBM channels, in accordance with an example of the present disclosure.

FIG. 11 is a block diagram of an example HBM buffer region in which each and every programmable IC interconnect channel has access to all the HBM channels, in accordance with an example of the present disclosure.

FIG. 12 is a block diagram of an example HBM buffer region with a hierarchical implementation of a switch network between the programmable IC interconnect channels and the HBM channels, in accordance with an example of the present disclosure.

DETAILED DESCRIPTION

Examples of the present disclosure provide techniques and apparatus for adding one or more features (e.g., high bandwidth memory (HBM)) to an existing qualified stacked silicon interconnect (SSI) technology logic circuit (e.g., a programmable integrated circuit (IC), such as a super logic region (SLR)) without changing the logic circuit (e.g., adding or removing blocks). The application interface and plug-in additions to the logic circuit (e.g., an HBM buffer and controller) may be designed on the same mask set as if these were a single die, with a standard scribe line separating the application plug-in portion of the logic circuit die and the interface die. The connection between the application plug-in and the interface die may be made over the scribe using interposer interconnections.

Example Integrated Circuit Package

An integrated circuit (IC) die is typically disposed in a package for electrical connection with a circuit board (e.g., a printed circuit board (PCB)). The package protects the integrated circuit die from potential physical damage and moisture, which may lead to corrosion.

FIG. 2 is a cross-sectional view of an example IC package 200 utilizing stacked silicon interconnect (SSI) technology. The IC package 200 includes a package substrate 202, an interposer 204 disposed above the substrate 202, a plurality of IC dies 206 disposed above the interposer 204, and an encapsulation material (not shown). The encapsulation material may be any of various suitable substances (e.g., resin) for encapsulating and protecting the IC dies 206. The IC dies 206 may include any of various suitable dies, including highly manufacturable field programmable gate array (FPGA) die slices, referred to as super logic regions (SLRs). Four IC dies 206 (IC0 to IC3) are illustrated in the example IC package 200 of FIG. 2, although the package may include more or less than four IC dies. SSI technology also allows dies of different types or silicon processes to be interconnected on the interposer 204.

The interposer 204 acts as an interconnect vehicle on which the IC dies 206 are set side by side and interconnected. The interposer 204 may be a passive silicon interposer, for example. Although only one interposer 204 is illustrated in FIG. 2, the IC package 200 may be implemented with multiple interposers in place of interposer 204 for some examples. The interposer 204 may include a plurality of interconnect lines 208, which may provide high-bandwidth, low-latency connections through the interposer 204. A plurality of microbumps 210 may be disposed above the interposer 204 for connecting electrically conductive pads of the IC dies 206 to the interconnect lines 208. The interposer 204 may also include a plurality of through-silicon vias (TSVs) 212 for routing connections between the IC dies 206 and a plurality of eutectic bumps 214 (e.g., controlled-collapse chip connection (C4) bumps) disposed between the interposer 204 and the package substrate 202. The TSVs 212 may provide the connections between the IC dies 206 and the substrate 202 for the parallel and serial I/O, power/ground, clocking, configuration signals, and the like. The plurality of eutectic bumps 214 electrically connect the interposer 204 to the substrate 202, and more particularly to conductive elements on the surface of and vias in the substrate.

The IC package 200 also has a plurality of solder balls 216 disposed below the package substrate 202. The solder balls 216 may be arranged, for example, in an array of rows and columns for making electrical contact with a matching arrangement of conductive pads disposed on a surface of a circuit board (e.g., a PCB).

Example Programmable Integrated Circuits

Many different types of integrated circuit (IC) dies 206 may be disposed on the interposer 204 and packaged in the IC package 200. One suitable type of IC is a programmable IC, such as a field programmable gate array (FPGA). An FPGA typically includes an array of programmable tiles. These programmable tiles may include, for example, input/output blocks (IOBs), configurable logic blocks (CLBs), dedicated random access memory blocks (BRAM), multipliers, digital signal processing blocks (DSPs), processors, clock managers, delay lock loops (DLLs), and so forth. Another type of programmable IC is the complex programmable logic device, or CPLD. A CPLD includes two or more “function blocks” connected together and to input/output (I/O) resources by an interconnect switch matrix. Each function block of the CPLD includes a two-level AND/OR structure similar to those used in programmable logic arrays (PLAs) and programmable array logic (PAL) devices. Other programmable ICs are programmed by applying a processing layer, such as a metal layer, that programmably interconnects the various elements on the device. These programmable ICs are known as mask programmable devices. The phrase “programmable IC” can also encompass devices that are only partially programmable, such as application-specific integrated circuits (ASICs).

FIG. 1 is a block diagram illustrating an example architecture 100 for a programmable device, which may be implemented in the IC package 200 of FIG. 2. The architecture 100 may be implemented within a field programmable gate array (FPGA), for example. As shown, the architecture 100 includes several different types of programmable circuitry, e.g., logic, blocks. For example, the architecture 100 may include a large number of different programmable tiles including multi-gigabit transceivers (MGTs) 101, configurable logic blocks (CLBs) 102, random access memory blocks (BRAMs) 103, input/output blocks (IOBs) 104, configuration and clocking logic (CONFIG/CLOCKS) 105, digital signal processing (DSP) blocks 106, specialized I/O blocks 107 (e.g., configuration ports and clock ports), and other programmable logic 108, such as digital clock managers, analog-to-digital converters (ADCs), system monitoring logic, and the like.

In some FPGAs, each programmable tile includes a programmable interconnect element (INT) 111 having standardized connections to and from a corresponding INT 111 in each adjacent tile. Therefore, the INTs 111, taken together, implement the programmable interconnect structure for the illustrated FPGA. Each INT 111 also includes the connections to and from the programmable logic element within the same tile, as shown by the examples included at the far right of FIG. 1.

For example, a CLB 102 may include a configurable logic element (CLE) 112 that can be programmed to implement user logic plus a single INT 111. A BRAM 103 may include a BRAM logic element (BRL) 113 in addition to one or more INTs 111. Typically, the number of INTs 111 included in a tile depends on the width of the tile. In the pictured example, a BRAM tile has the same width as five CLBs, but other numbers (e.g., four) can also be used. A DSP block 106 may include a DSP logic element (DSPL) 114 in addition to an appropriate number of INTs 111. An 10B 104 may include, for example, two instances of an I/O logic element (IOL) 115 in addition to one instance of an INT 111. As will be clear to a person having ordinary skill in the art, the actual I/O pads connected, for example, to the IOL 115 typically are not confined to the area of the IOL 115.

In the example architecture 100 depicted in FIG. 1, a horizontal area near the center of the die (shown shaded in FIG. 1) is used for configuration, clock, and other control logic (CONFIG/CLOCKS 105). Other vertical areas 109 extending from this central area may be used to distribute the clocks and configuration signals across the breadth of the FPGA.

Some FPGAs utilizing the architecture 100 illustrated in FIG. 1 include additional logic blocks that disrupt the regular row structure making up a large part of the FPGA. The additional logic blocks may be programmable blocks and/or dedicated circuitry. For example, a processor block depicted as PROC 110 spans several rows of CLBs 102 and BRAMs 103.

The PROC 110 may be implemented as a hard-wired processor that is fabricated as part of the die that implements the programmable circuitry of the FPGA. The PROC 110 may represent any of a variety of different processor types and/or systems ranging in complexity from an individual processor (e.g., a single core capable of executing program code) to an entire processing system having one or more cores, modules, co-processors, interfaces, or the like.

In a more complex arrangement, for example, the PROC 110 may include one or more cores (e.g., central processing units), cache memories, a memory controller, unidirectional and/or bidirectional interfaces configurable to couple directly to I/O pins (e.g., I/O pads) of the IC and/or couple to the programmable circuitry of the FPGA. The phrase “programmable circuitry” can refer to programmable circuit elements within an IC (e.g., the various programmable or configurable circuit blocks or tiles described herein) as well as the interconnect circuitry that selectively couples the various circuit blocks, tiles, and/or elements according to configuration data that is loaded into the FPGA. For example, portions shown in FIG. 1 that are external to the PROC 110 may be considered part of the, or the, programmable circuitry of the FPGA.

FIG. 1 is intended to illustrate an example architecture 100 that can be used to implement an FPGA that includes programmable circuitry (e.g., a programmable fabric) and a processing system. For example, the number of logic blocks in a row, the relative width of the rows, the number and order of rows, the types of logic blocks included in the rows, the relative sizes of the logic blocks, and the interconnect/logic implementations included at the right of FIG. 1 are exemplary. In an actual FPGA, for example, more than one adjacent row of CLBs 102 is typically included wherever the CLBs appear, in an effort to facilitate the efficient implementation of a user circuit design. The number of adjacent CLB rows, however, can vary with the overall size of the FPGA. Further, the size and/or positioning of the PROC 110 within the FPGA is for purposes of illustration only and is not intended as a limitation of the one or more examples of the present disclosure.

Example Standalone Interface for SSI Technology Integration

As described above, stacked silicon interconnect (SSI) technology devices use an interposer to connect multiple integrated circuit (IC) dies together using fine microbumps and metal traces much denser than what is available in conventional IC package technology or PCB technology. It may be desirable to take advantage of SSI technology for certain applications by connecting a fixed feature die (e.g., an ASIC) with an additional capability to a programmable IC die (e.g., an FPGA SLR) with connections substantially denser and faster than allowed using traditional I/O connected to package pins over a PCB. For some examples, if the additional capability is to be added to the programmable IC die, then additional circuitry (e.g., buffers) may need to be added to the programmable IC die that is connected to the fixed feature die to interface with the microbumps with a function and pattern consistent with the fixed feature die. For certain applications, the large number of additional connections it would take to support the new capability may be very disruptive to the programmable IC architecture, and may involve the removal of logic and/or DSP blocks and alterations to the clocking network. When such changes are made to an existing, working programmable IC die, it may be desirable to completely requalify the entirely die, which is complex and costly.

Examples of the present disclosure avoid this disruption and requalification of the programmable IC architecture and instead leave the programmable IC die unchanged. An interface die is designed that is compatible with the interposer interconnect data and clocking microbumps and interconnect pattern of the programmable IC die (e.g., an FPGA SLR) on one side and with the microbumps and interconnect pattern of the fixed feature die(s) on the other side. The interface die functions to convert the fixed feature protocol to an interposer interconnection compatible protocol. The programmable IC die and the interface die may share the same wafer-level substrate (e.g., the same monolith of semiconducting material) after wafer dicing, but may be separated by a scribe line (a standard scribe).

FIGS. 3A and 3B illustrate a top view and a cross-sectional view, respectively, of a portion of an example IC package (e.g., at the interposer level) comprising a programmable IC die 302 coupled to a fixed feature die 304 via an interface die 306, in accordance with examples of the present disclosure. A mask may be used to generate a wafer with the several instances of the programmable IC die 302 paired with the interface die 306. After dicing, the programmable IC die 302 and the interface die 306 may share the same wafer-level substrate, as illustrated in FIG. 3B. A scribe line 308 may separate the interface die 306 from the programmable IC die 302, and there may be no direct electrical connections between the two dies through the wafer section. Instead, a first set of interconnect lines 310 through the interposer 204 may be used to electrically connect circuits in the programmable IC die 302 and the interface die 306. One side of the interface die 306 is designed to be compatible with a pattern of the microbumps 210 and the first set of interconnect lines 310 for the programmable IC die 302. A second set of interconnect lines 312 routed through the interposer 204 may be used to electrically connect circuits in the fixed feature die 304 and the interface die 306. Another side of the interface die is designed to be compatible with a pattern of the microbumps 210 and the second set of interconnect lines 312 for the fixed feature die 304. In this manner, the design of the interface die 306 and the use of the interconnect lines 208 in the interposer 204 permit integrating the additional capability of the fixed feature die 304 into the SSI technology IC package, without any change to the programmable IC die 302. Therefore, an existing, working programmable IC die need not be requalified.

One example application that may utilize SSI technology includes High Bandwidth Memory (HBM). HBM is a high-performance random access memory (RAM) instance for three-dimensional (3-D) stacked dynamic RAM (DRAM), which may be used in any of various suitable applications, such as high-performance graphics accelerators and network devices. In HBM, up to eight DRAM dies may be stacked, which may be interconnected by through-silicon vias (TSVs) and microbumps.

HBM devices may take advantage of SSI technology to connect DRAM to a programmable IC die (e.g., an FPGA die) eight to ten times (8 to 10×) denser and faster than traditional DRAM allows using traditional I/O connected to package pins over a PCB. If HBM is to be added to an FPGA, then it may be desirable to add buffers to the FPGA that is connected to the HBM. These buffers would drive the microbumps with a function and pattern consistent with a neighboring HBM. The data coming from an HBM would have a very high bandwidth (e.g., 6 terabits per second (Tbps) per HBM device). Adding the tens of thousands of desired connections to the FPGA would be very disruptive to the FPGA architecture, involving removal of logic and DSP blocks from the regularity of the FPGA fabric to add connections from the HBM buffer. The addition may also disrupt the FPGA clocking network. Besides having to design a new HBM buffer, the IC manufacturer may also develop new blocks related to clocking, CLE, and/or DSP in an effort to add HBM support. As described above, the qualification of an FPGA (SLR) is very complex. Furthermore, it is expected that the HBM standard will change over the life of a typical FPGA product. A change to the standard may entail the redesign of the HBM buffer and the entire FPGA (SLR) and a complete requalification.

Examples of the present disclosure leave the FPGA (SLR) unchanged. An HBM buffer die may be designed that is compatible with the interposer interconnect data and clocking microbumps and interconnect pattern of the FPGA (SLR) on one side and with the microbumps and interconnect pattern of the HBM memory (or memories) on the other side. The function of the HBM buffer die is to convert HBM protocol to an interposer interconnect compatible protocol like AXI (Advanced eXtensible Interface). The FPGA and HBM buffer devices may share the same wafer-level substrate, but may be separated by a scribe line, as described above. Although an HBM application and an HBM buffer die are used as examples throughout the present disclosure, it is to be understood that any suitable application (and application-specific integrated circuit (ASIC) die) may be integrated in an SSI technology IC package using a suitable interface die.

FIG. 4 illustrates an example mask 400 for a pair of logic regions, in accordance with an example of the present disclosure. Each logic region includes a programmable IC die 402 and an HBM buffer die 404. Although a pair of logic regions are illustrated in the example mask 400 of FIG. 4, a mask may have only one logic region or more than two logic regions. FIG. 4 shows the programmable IC die 402 and the HBM buffer die 404 as having the same width 405 and being separated by a scribe line 406. This scribe line 406 may have a standard width. For other examples, the HBM buffer die 404 may have a different width than the programmable IC die 402. The HBM buffer die 404 and the programmable IC die 402 may have compatible interposer interconnect microbump patterns. The mask 400 in FIG. 4 may be used to make the wafers shown in FIGS. 5A and 5B.

FIGS. 5A and 5B illustrate how one mask set can be used to make two different logic regions. FIG. 5A is a top view of a wafer 500 with logic regions (e.g., SLRs) including programmable IC die 502 paired with an HBM buffer die 504, in accordance with an example of the present disclosure. The dashed lines 506 represent scribe cuts where the wafer 500 is diced, and the HBM buffer die 504 is separated from the programmable IC (PIC) die 502. The wafer 500 in FIG. 5A can be used to produce, for example, traditional SSI technology FPGA SLRs. The separated HBM buffer dies 504 may be discarded.

FIG. 5B is a top view of a wafer 520 with an HBM interface, in accordance with an example of the present disclosure. The wafer 520 may be the same starting wafer as the wafer 500 of FIG. 5A, but the scribe cuts are different. The wafer 520 in FIG. 5B is diced such that the PL die 502 and the HBM buffer die 504 are paired together as a single logic region (e.g., SLR). The HBM buffer and PL portions may be separated by a scribe and may not have any direct electrical connections in the diced wafer section. Rather, the connections between the two portions may be made by interconnect lines in the SSI interposer.

These interconnect lines 310 in the interposer 204 are designed to create wide, high-bandwidth connections between dies. Further, the interconnect lines 310 may be designed to distribute the bandwidth of the connection over enough of the programmable logic (e.g., FPGA) to absorb the astounding bandwidth of HBM. The separation (e.g., by a scribe line) of the programmable IC die and the HBM buffer die also serves to reduce the risk and increase vendor flexibility. In this manner, a problem with the HBM or HBM buffer die or a change in the HBM standard will not impact the usefulness of the programmable logic. Further, if the HBM design is changed due to HBM vendor differences or the evolution of the HBM standard, the programmable logic need not be disturbed. This will save an immense amount of qualification time, especially since the HBM-to-PIC connection over the interposer interconnect lines 310 may be soft and may not involve a mask change to modify. This soft connection over the interconnect lines 310 may be implemented with bidirectional drivers at the ends of each interconnect line, which can be controlled to adjust which lines are connected.

FIG. 6 illustrates a top view of a portion of an example IC package (e.g., at the interposer level) utilizing SSI technology, in accordance with an example of the present disclosure. The portion of the IC package includes a first logic region 602 (comprising a first programmable IC die) coupled to a second logic region 608 (comprising a second programmable IC die 604 paired with an HBM buffer die 606), where the second logic region may be referred to as a logic region with an HBM interface. The HBM buffer die 606 is coupled to two HBM dies 610, 612. Although the programmable IC die 604 and the HBM buffer die 606 are independent, these dies may be diced from a wafer as a single logic region 608. The two dies 604, 606 in the second logic region 608 may be connected using a first set of interconnection lines 614 routed through the interposer 615. The interconnection lines 614 routed between the programmable IC die 604 and the HBM buffer die 606 may be the same type as the interconnect lines 208 used between the IC dies 206 in FIG. 2. For some examples, the HBM channel may entail 1440 interconnect signals at 500 megabits per second (Mbps) with 8 channels per device. Thus, there may be 16 programmable IC interconnect channels with 1440 signals between the logic region 602 and the logic region 608. The interconnection lines 616 between the HBM buffer die 606 and the HBM dies 610, 612 may use the HBM JEDEC standard on the interposer 204. For some examples, there may be 212 interconnection lines per HBM channel at 2 gigabits per second (Gbps) with 8 channels per HBM device.

The interposer interconnections on a suitable process (e.g., 65 nm or smaller) may be very compatible with HBM bandwidth and density. FIG. 7 shows the top level design of an example HBM buffer die 700, in accordance with an example of the present disclosure. The HBM buffer die 700 may be one example implementation of the HBM buffer die 606 in FIG. 6. The signal count and bandwidth coming from the HBM die 610, 612 are nicely balanced by the interconnection signal bandwidth to the programmable IC (e.g., an FPGA). The circuit may have a switch network 702 (e.g., an AXI switch network) between the HBM channels 704 and the programmable IC interconnect channels 706. The HBM design also allows the HBM placement and the programmable IC interconnect placement to be independent.

Each master unit (MU) 708 in FIG. 7 may be, for example, a 512-bit AXI bus running at 500 MHz, which may take up most of the 1440 signals in a programmable IC interconnect channel 706. The slave unit (SU) 710 in each HBM output may also be, for example, a 512-bit AXI bus operating at 500 MHz. A HBM application of 128 bits at 2 gigabits per second (Gbps) may result in an AXI 512-bit interface at 500 MHz.

With examples of the present disclosure, HBM memory or another suitable capability can be added to an existing qualified SSI technology logic circuit without changing the logic circuit (e.g., adding or removing blocks). The application interface and plug-in additions to the logic circuit (e.g., an HBM buffer and controller) may be designed on the same mask set as if these were a single die, with a standard scribe line separating the application plug-in portion of the logic circuit die and the interface die. The connection between the application plug-in and the interface die may be made over the scribe using interposer interconnections.

There are numerous advantages provided by the standalone interface approach, according to examples of the present disclosure. Since programmable IC dies may have multiple tapeouts (e.g., engineering samples and production), the interface die (e.g., the HBM buffer die) can be added to any tapeout including production with no additional mask cost. Introducing support for additional features (e.g., HBM support) to a programmable IC (e.g., an FPGA) need not involve designing a new programmable IC and the subsequent modeling and qualification. Since interposer interconnections are already supported and modeled, adding capabilities (e.g., HBM) need not entail any additional work from various groups at the IC package designer and/or manufacturer. It may be possible for only one group to design the interface die (e.g., the HBM buffer die) knowing the design guidelines (e.g., the HBM standard) and the pattern for the interconnection signals on the programmable IC. The design may also be very portable to an outside vendor. Future changes to the design (e.g., revisions to the HBM standard) need not impact programmable IC design or qualification. The standalone interface design may be applied to any logic circuit with interconnect support.

Example Operations for Fabricating an IC Package

FIG. 8 is a flow diagram of example operations 800 for fabricating an IC package, in accordance with an example of the present disclosure. The operations 800 may be performed, for example, by a system for fabricating the IC package, which may include a semiconductor processing chamber.

The operations 800 may begin, at block 802, by providing a mask for a programmable IC die (or programmable IC region) paired with an interface die (or interface region). The interface die is for coupling the programmable IC die to at least one fixed feature die. At block 804, the mask is used to generate a wafer having a plurality of the paired programmable IC and interface dies. At block 806, the wafer may be diced to detach a wafer section comprising one of the plurality of the paired programmable IC and interface dies. At block 808, the wafer section may be disposed above an interposer comprising a plurality of interconnection lines. A first set of the interconnection lines may be routed through the interposer for electrically connecting the paired programmable IC and interface dies in the wafer section. A second set of the interconnection lines may be routed through the interposer for electrically connecting the interface die and the fixed feature die.

According to some examples, the operations 800 may further entail disposing the fixed feature die above the interposer. For some examples, the operations may further involve disposing the interposer above a package substrate and/or encapsulating the fixed feature die, the wafer section, the interposer, and at least a portion of the package substrate to form the integrated circuit package. For some examples, a plurality of microbumps may be disposed above the interposer. In this case, the plurality of microbumps may electrically connect the interconnection lines routed through the interposer with circuits in the programmable IC die, the interface die, and the fixed feature die. For some examples, the interface die in the wafer section is compatible with a first pattern of the microbumps and the first set of interconnection lines for the programmable IC die and compatible with a second pattern of the microbumps and the second set of interconnection lines for the fixed feature die.

According to some examples, the operations 800 may further include forming a scribe line between the programmable IC die and the interface die in each of the paired programmable IC and interface dies.

According to some examples, the paired programmable IC and interface dies in the wafer section share the same wafer-level substrate.

According to some examples, the fixed feature die comprises an HBM die. In this case, the interface die may comprise an HBM buffer die. For some examples, the second set of interconnection lines is in accordance with the HBM JEDEC standard.

According to some examples, the fixed feature die comprises an application-specific integrated circuit (ASIC).

According to some examples, there are no electrical connections between the paired programmable IC and interface dies in the wafer section, other than through the interconnection lines routed through the interposer.

Example HBM Bandwidth Aggregation Switch

As described above, HBM is a high-performance RAM instance for 3-D DRAM, which may be used in any of various suitable applications, such as high-performance graphics accelerators and network devices. In HBM, up to eight DRAM dies may be stacked, which may be interconnected by through-silicon vias (TSVs) and microbumps. HBM devices may take advantage of SSI technology to connect stacked DRAM to a programmable IC die eight to ten times (8 to 10×) denser and faster than traditional DRAM allows using traditional I/O connected to package pins over a PCB. One HBM device can have 16 pseudo memory channels, each with the same bandwidth as a 1600 Mbps 64-bit double data rate (DDR) dual in-line memory module (DIMM), which is a considerably high bandwidth.

However, each memory channel in HBM goes to an isolated memory array, and each HBM channel can only access memory with addresses in its partition. To fully utilize all bandwidth and bits of an HBM device, a system may have, for example, 16 independent agents accessing each channel. If a system in the programmable IC has only four agents, it may be very difficult to connect groups of channels to each agent to use all bits and bandwidth. The aggregation of HBM channels to each agent may employ substantial fabric resources in the programmable IC, which may be made more challenging by the bandwidth requirements of HBM. Without an HBM switch (e.g., the switch network 702), each HBM pseudo channel may be connected to the programmable IC fabric through an interface between the fabric logic and other logic and input/output (I/O) on the boundary of the programmable IC die (referred to as a boundary logic interface (BLI)). The BLI may allow the very large and complex HBM pseudo channel logic and I/O to be perceived as a much smaller block, such as a CLE or DSPL (e.g., CLE 112 or DSPL 114 in FIG. 1) in the fabric array of the programmable IC.

Examples of the present disclosure utilize a switch (e.g., switch network 702) between the programmable IC interconnect channels (e.g., FPGA BLI) and the HBM pseudo channels (PCs). For some examples, the switch may allow any programmable IC interconnect channel to access any HBM pseudo channel(s). Therefore any interconnect channel could access any bit in the HBM, regardless of from which pseudo channel the bit is accessed.

In the current PCB-based design environment, having four 64-bit DDR DIMMs pushes the limit of package and PCB technology. For some examples, a programmable IC with HBM may allow the equivalent of sixteen 64-bit DDR DIMMs connected thereto. It is likely that some customers and applications will find a use for 16 HBM interfaces, but most applications will continue to use 4 interfaces or may double this to 8. Thus, a customer desiring 4 memories may combine the bandwidth and bits of 4 HBM pseudo channels to make a virtual memory. It is to be understood that many combinations are possible, from four groups of 4 to one group of 13 and three groups of 1, etc. Each HBM pseudo channel (PC) may enter the fabric region of the programmable IC through a BLI, which may be a 256-bit full duplex AXI bus running at 500 MHz. Combining four HBM pseudo channel BLI may consume significant resources of the programmable IC and may have very difficult timing closure. Hardening a switch between the programmable IC interconnect channels (e.g., FPGA BLI) and the HBM PCs may save fabric resources and remove timing closure issues.

There are two major characteristics that an ideal switch network should have. First, in an idyllic case, every BLI master input to the switch network has access to any and all HBM pseudo channel slave ports. Second, in the case where each BLI is connected directly to one and only one HBM PC (also referred to as “the affinity case”), the latency through the switch network should be minimal.

FIG. 9 is a block diagram of an example HBM buffer region 900 for the affinity case, in accordance with an example of the present disclosure. The circuit may have a switch network 902 between the HBM channels 704 (e.g., HBM PCs) and the programmable IC interconnect channels 906 (e.g., BLI ports). In the switch network 902, each programmable IC interconnect channel 906 is connected to directly to one and only one HBM channel 704.

The affinity case of FIG. 9 is an application that uses the maximum bandwidth available from the HBM device(s). An application using the affinity case may expect the minimum latency possible. For other HBM buffer regions described below, it may be an option to effectively bypass the switch for minimum latency by configuring the switch network 902 to operate in the affinity case illustrated in FIG. 9.

Similar to other examples described above, the HBM buffer regions described herein (including HBM buffer region 900) may be compatible with the interposer interconnect data and clocking microbumps and interconnect pattern of the programmable IC on one side and with the microbumps and interconnect pattern of the HBM memory (or memories) on the other side. The function of the HBM buffer region is to convert HBM protocol to an interposer interconnect compatible protocol like AXI (Advanced eXtensible Interface). For some examples, the programmable IC and HBM buffer region 900 may share the same wafer-level substrate, but may be separated by a scribe line and rely on an interposer for connection therebetween, as described above. In this case, the HBM buffer region 900 may be a separate HBM buffer die. For other examples, the HBM buffer region 900 may be integrated with the programmable IC in a single, monolithic die. In this case, the programmable IC and HBM buffer need not rely on the interposer for connection therebetween, and there may be no electrical connections routed through the interposer to connect the programmable IC and the HBM buffer, for some examples. Instead, IC metallization may be used to connect the HBM buffer circuitry with the programmable IC circuitry. The IC metallization may utilize one or more metallization layers. For other examples, a combination of IC metallization and interposer interconnect lines may be utilized to connect the programmable IC circuitry with the HMB buffer circuitry.

The switch network 902 may be, for example, an AXI type switch network or a packet-protocol type switch network. In an AXI type switch network, signals may be driven from each master unit 708 and multiplexed onto a common address/data/control bus by a multiplexer (MUX) controlled by an arbiter. The output of the multiplexer may be fanned-out to the slave units 710. The bus transfers data, address, and control signals separately through the MUX structure. The address and control along with the arbitration system directs data buses through a series of MUXes and buffers from a master unit 708 to a slave unit 710. In a packet-protocol type switch network, data, address, and control may be combined in a packet with a set of flow control digits (also referred to as “flits”). The packet may be sent, for example, from a master unit 708 to a slave unit 710 based on the flits.

FIG. 10 portrays an example HBM buffer region 1000 in which the switch network 902 is configured such that one programmable IC interconnect channel 906 _(A) has access to all the HBM channels 704, in accordance with an example of the present disclosure. In this manner, this particular channel 906 _(A) has full addressability. However, the bandwidth may be limited by the BLI port and not by the HBM PC in this case. It is to be understood that the particular programmable IC interconnect channel can be any one of the interconnect channels 906 in other examples.

FIG. 11 depicts an example HBM buffer region 1100 in which the switch network 902 is configured such that each and every programmable IC interconnect channel 906 has access to all the HBM channels 704, in accordance with an example of the present disclosure. Referred to as a “full crossbar switch,” this type of switch can implement both cases illustrated in FIGS. 9 and 10 and all combinations in between. Although a full crossbar switch is extremely flexible, it has two drawbacks. First, the full crossbar switch would have a very large implementation to realize the various combination of access paths, even if implemented as a hard block. Second, the latency of all paths including the affinity case would be relatively high (i.e., slow paths), such that the full crossbar switch would have considerable latency.

One alternative to the full crossbar switch is a hierarchical switch. FIG. 12 illustrates an example HBM buffer region 1200 in which the switch network 902 is configured to implement a hierarchical switch between the programmable IC interconnect channels 906 and the HBM channels 704, in accordance with an example of the present disclosure. In this example implementation, the hierarchical switch comprises two 5:5 full crossbar switches 1210 and two 6:6 full crossbar switches 1212, with cross-coupled connections 1214 between adjacent full crossbar switches. The arrangement still offers the affinity case of FIG. 9 and the full addressability case of FIG. 11. Although two 5:5 full crossbar switches 1210 and two 6:6 full crossbar switches 1212 are illustrated in FIG. 12, it is to be understood that any of various suitable full crossbar configurations may be used to implement a hierarchical switch in the alternative (e.g., two 9:9 full crossbar switches, or two 3:3 full crossbar switches and six 4:4 full crossbar switches). The full addressability case latency for the hierarchical switch is a function of the number of switches cascaded between the programmable IC interconnect channels 906 and the HBM channels 704. The affinity case with the hierarchical switch has significantly less latency since a 6:6 full crossbar switch has significantly less latency than a 16:16 full crossbar switch (illustrated in FIG. 11).

In the flexible implementation of FIG. 11, the full crossbar switch provides a “dedicated” path between every master unit 708 and slave unit 710. Therefore, there is no blocking. In contrast, the hierarchical switch of FIG. 12 has some blocking. One example of blocking is a case where two of the master units 708 in the leftmost 5:5 full crossbar switch 1210 want to access two slave units 710 in the leftmost 6:6 full crossbar switch 1212. In this case, both paths through the switch network 702 would share one of the cross-coupled connections 1214 between the leftmost 5:5 and 6:6 full crossbar switches 1210, 1212. Since two master units 708 cannot concurrently use the same resource, one of the paths is said to “block” the other path's access to a slave unit 710 in the leftmost 6:6 full crossbar switch 1212.

To avoid blocking, a number of strategies may be employed. One strategy entails having a good scheduler that sequences the master units 708, such that one master unit does not block another. Another strategy involves using buffers at congestion points (e.g., at the cross-coupled connections 1214). With buffers, a subsequent data set received by a switch can be buffered until the switch resource is free (e.g., a previous data set received by the switch has been cleared out).

Based on the examples presented above, examples of the present disclosure offer countless switch implementations with good affinity latency and full addressability from any channel with minimal blocking and latency characteristics. Furthermore, some example switch implementations may provide an affinity bypass mode. The affinity bypass mode may offer an affinity case with the lowest possible latency, independent of the switch architecture.

Revisiting the operations 800 of FIG. 8, the programmable IC die and the interface die may instead be a programmable IC region and an interface region. As described above for some examples, the interface region may be integrated with the programmable IC region in a single, monolithic die, while in other examples, the programmable IC region and the interface region may be separate dies (e.g., sharing the same wafer-level substrate, but separated by a scribe line for some examples). Instead of disposing the wafer section above an interposer at block 808 as described above, the operations 800 may alternatively involve disposing the wafer section above an interposer, wherein a first set of interconnection lines is routed through the interposer for electrically coupling a first plurality of ports of the interface region and the fixed feature die and wherein a second set of interconnection lines electrically couples a second plurality of ports of the interface region to the programmable IC region of the paired programmable IC and interface regions in the wafer section.

According to some examples, at least a portion of the second set of interconnection lines is routed through the interposer.

According to some examples, the programmable IC region and the interface region are part of a monolithic die. In this case, the second set of interconnection lines may be routed through at least one metallization layer of the monolithic die. For some examples, none of the second set of interconnection lines is routed through the interposer.

According to some examples, the operations 800 may further entail disposing the at least one fixed feature die above the interposer. In this case, the operations 800 may further involve disposing the interposer above a package substrate and encapsulating the at least one fixed feature die, the wafer section, the interposer, and at least a portion of the package substrate to form the integrated circuit package.

According to some examples, the interface region is capable of configuration as a switch network between the first plurality of ports and the second plurality of ports. For some examples the switch network provides full addressability between each of the first plurality of ports and each of the second plurality of ports such that each of the second plurality of ports has access to any one of the first plurality of ports. For some examples, the switch network provides a bypass mode in which each of the second plurality of ports has access to a different one of the first plurality of ports. For some examples, the switch network is implemented as a hierarchical switch network, which may be composed of a plurality of connected full crossbar switch networks. For some examples, the switch network is implemented as an AXI type switch network. For other examples, the switch network is implemented as a packet-protocol type switch network.

According to some examples, the operations 800 further include forming a scribe line between the programmable IC region and the interface region in each of the paired programmable IC and interface regions.

According to some examples, the fixed feature die is an HBM die. In this case, the interface region may be an HBM buffer region, and the first plurality of ports may include HBM channels (e.g., HBM PCs). The second plurality of ports may include programmable IC interconnect channels.

As used herein (including the claims that follow), a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: x, y, and z” is intended to cover: x, y, z, x-y, x-z, y-z, x-y-z, and any combination thereof (e.g., x-y-y and x-x-y-z).

While the foregoing is directed to examples of the present disclosure, other and further examples of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

What is claimed is:
 1. An integrated circuit (IC) package comprising: a package substrate; at least one interposer disposed above the package substrate; a programmable IC region disposed above the interposer; at least one fixed feature die disposed above the interposer; and an interface region disposed above the interposer and configured to couple the programmable IC region to the fixed feature die via a first set of interconnection lines routed through the interposer between a first plurality of ports of the interface region and the fixed feature die and a second set of interconnection lines routed between a second plurality of ports of the interface region and the programmable IC region, wherein the interface region is configured as a switch network between the first plurality of ports and the second plurality of ports.
 2. The package of claim 1, wherein the switch network provides full addressability between each of the first plurality of ports and each of the second plurality of ports such that each of the second plurality of ports has access to any one of the first plurality of ports.
 3. The package of claim 2, wherein the switch network provides a bypass mode in which each of the second plurality of ports has access to a different one of the first plurality of ports.
 4. The package of claim 2, wherein the switch network is implemented as a hierarchical switch network comprising a plurality of connected full crossbar switch networks.
 5. The package of claim 1, wherein the switch network is implemented as an Advanced eXtensible Interface (AXI) type switch network.
 6. The package of claim 1, wherein the switch network is implemented as a packet-protocol type switch network.
 7. The package of claim 1, wherein the programmable IC region and the interface region are part of a monolithic die and wherein the second set of interconnection lines is routed through at least one metallization layer of the monolithic die.
 8. The package of claim 7, wherein none of the second set of interconnection lines is routed through the interposer.
 9. The package of claim 1, wherein: at least a portion of the second set of interconnection lines is routed through the interposer; and the programmable IC region and the interface region share the same wafer-level substrate and are separated on the wafer-level substrate by a scribe line.
 10. The package of claim 1, wherein the programmable IC region comprises a field programmable gate array (FPGA) region.
 11. An integrated circuit (IC) package comprising: a package substrate; at least one interposer disposed above the package substrate; a programmable IC region disposed above the interposer; at least one fixed feature die disposed above the interposer; and an interface region disposed above the interposer and configured to couple the programmable IC region to the fixed feature die via a first set of interconnection lines routed through the interposer between a first plurality of ports of the interface region and the fixed feature die and a second set of interconnection lines routed between a second plurality of ports of the interface region and the programmable IC region, wherein the programmable IC region comprises a field programmable gate array (FPGA) region, wherein the fixed feature die comprises a high bandwidth memory (HBM) die, wherein the interface region comprises an HBM buffer region, and wherein the first plurality of ports comprises HBM channels.
 12. The package of claim 11, wherein the programmable IC region and the interface region are part of a monolithic die, share the same wafer-level substrate, and are separated on the wafer-level substrate by a scribe line.
 13. The package of claim 11, wherein the interface region is configured as a switch network between the first plurality of ports and the second plurality of ports.
 14. A method of fabricating an integrated circuit (IC) package, comprising: providing a mask for a programmable IC region paired with an interface region, the interface region for coupling the programmable IC region to at least one fixed feature die; generating, using the mask, a wafer having a plurality of the paired programmable IC and interface regions; dicing the wafer to detach a wafer section comprising one of the plurality of the paired programmable IC and interface regions; and disposing the wafer section above an interposer, wherein a first set of interconnection lines is routed through the interposer for electrically coupling a first plurality of ports of the interface region and the fixed feature die and wherein a second set of interconnection lines electrically couples a second plurality of ports of the interface region to the programmable IC region of the paired programmable IC and interface regions in the wafer section.
 15. The method of claim 14, further comprising: disposing the at least one fixed feature die above the interposer; disposing the interposer above a package substrate; and encapsulating the at least one fixed feature die, the wafer section, the interposer, and at least a portion of the package substrate to form the integrated circuit package.
 16. The method of claim 14, wherein the interface region is capable of configuration as a switch network between the first plurality of ports and the second plurality of ports.
 17. The method of claim 16, wherein the switch network provides full addressability between each of the first plurality of ports and each of the second plurality of ports such that each of the second plurality of ports has access to any one of the first plurality of ports.
 18. The method of claim 16, wherein the switch network provides a bypass mode in which each of the second plurality of ports has access to a different one of the first plurality of ports.
 19. The method of claim 14, further comprising forming a scribe line between the programmable IC region and the interface region in each of the paired programmable IC and interface regions.
 20. The method of claim 14, wherein the fixed feature die comprises a high bandwidth memory (HBM) die, wherein the interface region comprises an HBM buffer region, and wherein the first plurality of ports comprises HBM channels. 